Dark Guardian
by o0Golden-Moon0o
Summary: Tsuna had been running since he was five searching for the meaning of his life. Who knew that a deathly game such as SAO would give him everything he was looking for? [WARNING: Slash]
1. Chapter 1

**Epilogue**

 **Summary:** Tsuna had been running since he was five searching for the meaning of his life. Who knew that a deathly game such as SAO would give him everything he was looking for?

A story about how Tsuna reacts to the Mafia world after having experienced SAO together with his Dark Night.

 **Pairing: Kirito/Tsuna**

 **Disclaimer:** _Nor Katekyō_ _Hitman Reborn or Sword Art Online belong to me. I just enjoy playing around and eating virtual cookies/reviews in exchange. ^.^_

 **Beta:** CreepyAlis-SAMA _(= plz tell me if I missed anything, ok? Thanks_ ~)

 **A.N.**

I really hope you enjoy. I adore both Katekyō _Hitman Reborn and Sword Art Online and I decided to see what would've happened if I mixed them together._

 _SAO will be AU. I love Asuna, but I wanted to experiment a bit by matching Kirito with someone else (like cute Tsuna for example…) since there are so little alternative parings._

 _Tsuna will be very OC obviously because one cannot experience something as Aincard without changing._

 _Nothing but fluff will happen between Kirito and Tsuna for a bit because Tsuna is still young, but the two will be very tied together and already love each other._

 _So without further ado, on to the story! I present thy the_ _ **Dark Guardian**_ _!_

* * *

 _Red, blood, a laughter, cheers, dread, happiness, a vortex of distorted colors, dizziness and then darkness._

He- no, _they_ had managed. Finally they had escaped from that nightmare. No more death and grief. All thanks to his Dark Night. He panicked. Kirito! Kirito had disappeared after defeating that monster! He had to see if he was all right! He started struggling but he couldn't manage to move his body. It was as if his limbs were made of stone.

He felt a faraway voice telling him to calm down and that everything was alright. He slowly started to follow that voice from the darkness of his mind and opened his eyes. He regretted it immediately. The light was blinding and he was forced to close them shut again. The voice told him to take it slowly. Tsuna obeyed and managed to open his eyes without pain. He instinctively looked around to catalog the room and its possible threats. It was a normal blinding white hospital room with little furniture (just a bed side table) but with quite a lot of futuristic hospital machines attached to his body, all beeping or flashing different light colors. A doctor was next to him with his medical board and was checking the machines' data. Seeing him finally awake the doctor smiled.

"Hallo, Tsunayoshi-kun, I am Doctor Tsubaki. How do you feel? Are you sore anywhere?" Dr. Tsubaki asked him kindly.

He frowned and thought about it. He wasn't in pain, he actually felt quite good. The virtual world was supposed to be less real because it couldn't imitate completely reality's sensations but to him it had always felt sharper and he had actually managed to think clearly there.

It hadn't always been like that. He recalled a distant memory of a bright, stunning, colorful, deliciously warm and beautiful world before that deceiving Troll had stole it from him with just a touch on his forehead. It was one of the many reasons he resented his father. He had passively allowed that old man ("call me Nono, Tsunayoshi-kun") to do as he pleased and then hardly cared when he had pleaded him to give him back that amazing world. His _father_ only looked at him with uncaring eyes and dismissed him saying he was just confused and to stop lying. He went away shortly after and only interacted with him and his mom through the phone.

" I'm not sore but I can't move." He finally answered.

The doctor explained that it was normal as it had been 4 years since he had moved. He then proceeded to ask if he could remember who he was and if he could recall his real life. After answering the seemingly endless questions he was asked, Dr. Tsubaki told him to rest and that tomorrow he could see his mother.

As soon as he went away, Tsuna managed to sit up and moving his arm painstakingly slowly he reached for the phone on the side table. He dialed the numbers he had learnt by heart with a trembling hand and waited. He was starting to panic when the line connected.

"Hello?"

He instantly calmed, his tense muscles relaxed and he melted in the hospital bed clutching the phone tightly with both hands. The voice was a bit raspy but he could recognize it everywhere.

"Kirito, it's me Tsuna" He actually hadn't realized how tense he was until now. Kirito's voice was the confirmation that everything was alright.

"Tsuna! Where are you? Are you alright?" Kirito's voice distracted him from his musings.

"Yes. I'm in Namimori's Central Hospital. The doctor said I have to regain muscle mass, but other than that everything seems fine. I'm supposed to see mom tomorrow. Are you feeling ok?!"

He was quite concerned. After all Kirito had been the player who overworked himself the most. Especially after Sugō had taken over after Kayaba's death and had coerced everyone to clear all a hundred floors to be free.

His distress must have been heard because Kirito chuckled over the phone.

"Little Healer, I'm fine, don't worry. I'm in my room. Well what was once my room, now it looks like a spaceship with all these noises and lights. A doctor passed by and told me I just have to take it easy for a while and spend some time in rehabilitation. " Kirito's voice lulled him and he yawned.

"Alright there it's time for a nap" Kirito interrupted his protests before they even started "you can phone me again tomorrow, I'm not going anywhere. We both need rest"

Tsuna grumbled but acquiesced. After a goodbye he put down the phone and cuddled in the thin hospital blankets. He soon fell asleep.

* * *

 _He was in the 22_ _nd_ _floor in the vacation house Kirito had bought._

 _He was relaxing on the comfy sofa after a hard battle against the 46 floor boss. As usual the Black Knight had won but it was getting more and more difficult to clear the floors' dungeons without help. Kirito was very strong (the strongest if you asked him) and while he could fight quite decently himself (who wouldn't after Kirito's training) his strength lied in Healing. The game didn't have magic but he had managed to finish a quest that had awarded him Caliburnium, the sister of Excalibur. While Excalibur was forged by Merlin and was known for being the sword Arthur had used in battle thus making him invincible, Caliburnium was a sword that possessed a quite elegance, it was said to come from Avalon, its power was to heal from all kinds of illness, wound or poison._

 _The sword turned out to be a miracle because the more he leveled it the more it allowed him to heal. He had reached such a mastery of it that he was able to restore all one's HP for 2 times even if it hit 0. If it weren't for her he and Kirito probably wouldn't have lasted so long alone._

 _"_ _What are you thinking about?" a voice near his right year asked._

 _He jumped, not having felt Kirito's approaching. He took advantage of Kirito's laughing to catch him unaware and chuck the first cushion he found to his face. He hadn't considered that he was hugging him and therefore Kirito dragged him on top of him on the floor. He squawked as he fell and the annoying smug swordsman was still laughing! Tsuna pouted and hit him again with the cushion. After a while (too much if you asked Tsuna) Kirito stopped laughing and hugged him. Tsuna snuggled into his embrace. It were times like these that made him think that even if some could call this world hell, he couldn't bring himself to consider it such just because he had met Kirito._

* * *

 ** _A.N._** _Tell me if you're interested in seeing Asuna in this story and if yes, if you want her paired with someone (who?). Please feed me cookies/reviews? *puppy dog eyes maximum power*  
_


	2. Chapter 2

**Chapter one**

 **Summary:** Tsuna had been running since he was five searching for the meaning of his life. Who knew that a deathly game such as SAO would give him everything he was looking for?

A story about how Tsuna reacts to the Mafia world after having experienced SAO together with his Dark Night.

 **Pairing: Kirito/Tsuna**

 **Disclaimer:** _Nor Katekyō_ _Hitman Reborn or Sword Art Online belong to me…Yet. As soon as I become the ruler of the world everything shall belong to me! Muahahahahaha!_

 _I'm joking, I'm joking. (or maybe not! BEWARE MORTALS!)_

 **A.N.**

Another chapter! YAY! I hope you'll like it!

 **Beta:** CreepyAlis-SAMA [a.k.a. Future co-ruler of your world~] _(= plz tell me if I missed anything, ok? Thanks_ )

 _Dreams/flashbacks_

* * *

Tsuna woke up slowly, savoring the warmth that his (not) very cozy bed provided him.

In the game he had had to appoint himself a code. Beds signified safety and comfort, meaning he didn't need to be wary of the situation nor become alert immediately, but he was allowed to take it easy. Bumpy, hard ground instead implied danger and necessary alertness. It was a very difficult code to follow because he had always loved to laze in bed for an inordinate amount of time, but it soon become clear how incredibly useful it was.

Leisurely he started to recall where he was. In his semi-conscious mind he realized something was... He couldn't pinpoint it. Certainly not wrong… it felt strange, different.

He jumped, suddenly completely aware. Yesterday he hadn't been very aware if he had only considered peripherally how sharply he felt!

Everything was amplified. He could feel every crease of his sheets, every sound was sharp and distinct, he could smell the different medicines and detergents... and his sight! He could see everything perfectly! Every color was bright making the world seem impossibly alive. The white in the room, he previously thought as monochromatic and blinding, was in reality composed by thousands of different shades, creating an astonishing canvas. The view outside the window was not a simple courtyard with a thin and young tree but a composition of colors melding together, the golden rays coming from the sun made every tiny thing shine as if it possessed an inner light that accentuated its beauty. Tsuna's fingers itched for colored pencils and a piece of paper so that he could capture the beauty and magnificence in front of him.

He stared stunned around him until he realized that something else had changed. He frowned and concentrated, trying to separate it from the newly attained sensations.

It was hard but after a while he realized that while his sensations were related to the outside world, this feeling came from inside his body. It was something he had lived with since he was five but had been able to forget for 3 years. It was a state of being, complex to explain fully and difficult to understand even for himself. He had began to associate it to how drowning felt like. Ice cold water surrounding his very being. The terrible cold that had insinuated itself into every nook of his body and had filled him completely, changing him irremediably. Everything he did was like moving underwater. Everything was slower, duller, harder and unclear. He hadn't been able to think normally anymore, every thought in his brain floated difficultly as if it had to show itself to him from a haze, he couldn't move properly anymore, his reactions were dangerously slow, he tripped everywhere and couldn't coordinate his movements at all.

The only escape he had had were his dreams and drawings, filled with colors and life.

He had finally manged to escape from that haunting sensation in SAO which somehow gave him back a part of his missing world. He hadn't realized he had been missing so much though.

The warmth had returned. The wonderful warmth he linked to happiness, freedom and life.

He concentrated harder, trying to catalogue how it worked. It moved, he realized, it moved lazily and sinuously. He tried reaching it and directing it to his fingers. It answered his call like an eager kitten, following his order swiftly and leaving a trail of warmth from his lower belly to his hands. Surprisingly it was very easy to play with. He tried directing it towards various parts of his body. When he deviated it towards his eyes, ears or nose though he immediately retracted it. He had just started getting used to his new sharpened senses, he couldn't endure an additional increase of their strength!

* * *

He had experimented with it for a while until a knock broke his concentration and he lost contact with it. He panicked, thinking for a second he had lost the warmth again but soon relaxed feeling it just underneath his skin, ready to obey his will and to cuddle with him again.

"You may come in" He said timidly.

Dr. Tsubaki entered looking at his clinical board.

"How are you feeling today?" He asked, while writing something down.

"Much better" He answered politely.

Dr. Tsubaki looked up from his board and his eyes widened in astonishment.

"I see you managed to sit up on your own! Very good! This is an incredible improvement!"

He hurriedly wrote something else on his board.

"Now, your mother is waiting outside. Do you feel like seeing her? If you are not up to it it's all right, after all you must be still quite tired"

He had conflicted feelings towards his mother.

When he had met Asuna-nee she had promptly started pampering and caring for him exuberantly. At first he was totally overwhelmed by the attention, so different from Kirito's quiet, steady and strong presence or his mom's distant, distracted and volatile one. As time passed however he started to get used to it and finally understood that neglecting one's son for days and forgetting about feeding him like his mother had done, in more than one occasion, was definitely not normal.

But she was his mother after all and he was sure she had been worried sick.

* * *

He retreated his previous statement. Immediately.

After having fussed a bit at his thinness promising she would cook some food for him, she started talking to him about her a new friend here a new sale there, gushing about _father_ 's 3 phone calls and so on. He had been trapped in that virtual reality for three years and Iemitsu had only called 3 times! And apparently he didn't even know he was a SAO player. He managed to infer from her blabbering that she hadn't told his father about his situation and that she had asked for a confidential contract to be signed by all the medical staff working to his case. She had money after all, Iemitsu may not come home very usually (never) but he sent a conspicuous amount of money every month. She had kept his condition under the wraps because he shouldn't have been allowed to play having been only 10. His mother had decided to buy the shining new game for his birthday without even checking the age limit and therefore once he had been trapped she hadn't had the courage to tell his _father_ about it.

By her chattering he gathered that her life hadn't changed much since his forced sleep. He was starting to feel nausea and was about to call for a nurse and request her to be sent away.

He tried calming down and suddenly realized she was acting strangely. She was tense, her hands were trembling and she couldn't look at him in the eyes. Realization hit him. Maybe he had been too harsh towards her, she was probably just reacting in the only way she knew.

He sighed, impulsively grabbed her hand and tugged it like he used to do when he was a child and wanted a hug. She just followed his silent request, wrapped her arms around him and squeezed hard. She started trembling, hid her face in his neck and immediately after started crying and asking for forgiveness.

Tsuna closed his eyes and caressed her hair. She wasn't a bad person, he knew, she was just a bad mother.

"It's ok mum, I'm ok, I'm here". Like that all his resentment had vanished.

He still loved her.

* * *

As soon as his mother went away with the promise of a cooked meal, the doctor came in again and detached all the machines from his body. He looked at him considering and then asked him if he felt like trying to walk. He immediately accepted. The faster he could move, the faster he could escape this boring hospital. He managed five steps. He almost fell if it weren't for Dr. Tsubaki's help. The doctor seemed rather surprised and told him he was in a much better shape than most of SAO survivors. After taking some blood samples, and promising him a tablet to read so he wouldn't become so bored, he went away.

After a while a nice nurse came in with the promised tablet. She was about to leave the room but something in his face must have told her how completely lost he was.

How much did technology evolve in these 3 years!? He expected a small screen with a rudimental graphic interface, instead he got a huge one with a resolution that seemed so real for an instant he had thought he was looking out of a window. He had absolutely no idea on how to use it! He was even afraid to touch it, how much would it cost him if he broke it!

The nurse took pity of him and stayed for a while, teaching him how to use it. It turned out to be pretty easy and soon he was surfing the internet starting to catch up on everything he had lost.

His first priority was to learn what had happened after Hearthcliff's defeat. After all Kayaba had promised he would free them all after his loss.

Apparently a very greedy, named Sugō Nobuyuki, had wanted to marry the daughter of the rich Yūki Family, but had been rejected. He had infiltrated into the servers of Cardinal System and had blocked the players' log out.

All to take revenge on Asuna and her parents!

He had wanted to blackmail the Yūki's and although he had been arrested immediately, he had managed to trap every SAO player. The only escape was to complete all the 100 floors of Aincrad.

* * *

At lunch time, after being forced to eat disgusting hospital food, the nurse who had taught him how to use the tablet told (ordered) him to have a nap. He reluctantly obeyed, just because he was feeling a bit worn out.

* * *

 _The red had bled into the sky, turning the plaza he had been forcibly transported to into a horror film. The calm voice of the creator was so surreal. He couldn't understand how someone could be so calm and collected while announcing the end of the life of hundreds human beings and admit he was the cause of the beginning of an era of death. As the terrifying announcement continued he could feel all of his body starting to tremble increasingly._

 _He couldn't move, couldn't think, couldn't even look around him. He was completely paralyzed._

 _Something appeared in his hand automatically and he felt his body shrink from its teen like appearance, his muscles diminish from those of a powerful warrior he had created to those of a normal 10 year old and his hair lighten to its normal honey blond._

 _He noticed all this in a remote part of his brain, distantly he could also feel the other players around him yelling, running away to reach something that didn't exist._

 _He could feel something was wrong with his reaction, he should move, scream, ask for help like everyone was doing but... he couldn't react at all! He knew that whatever he did was all useless._

 _He needed to find a quite place to clear his mind, decide what to do._

 _He slowly started reconnecting with reality and discovered he was hyperventilating. He concentrated on his breathing and decided he had escape from all the chaos. He ordered his legs to move toward one of the many alleys that branched from the square._

 _It was already occupied by other two players. They seemed to be discussing softly. It took him a moment to become conscious that something was odd._

 _He realized suddenly that it was like looking at another reality, all the confusion he had seen up till now was completely absent, they both seemed calm and collected. Even if he could only see Dark's back, he could see that he was even more composed than Red. The abnormality of the scene had shocked him still and when Red focused on him, he couldn't even bring himself to escape. Strangely he seemed very astounded by his presence. Almost as if Red were scared, not of him but for him._

" _You could take him, he certainly needs more help than I do" Red broke the tense silence. Dark turned, his eyes widened a fraction and then narrowed, looking at him considering. He started walking towards him and at first Tsuna thought he was going to attack him and tensed, but when he was in front of him Dark crouched down and looked at him the eyes. The surprising gesture put him immediately at ease even if he couldn't understand what was going on._

" _Would you like to stay here in the city, safe from harm, or come with me? If you chose to come know that your future will be filled with danger, terrifying and difficult but I will look after you at the best of my abilities. I will fight until I manage to beat this game and escape."_

 _Tsuna was about to laugh hysterically, who would be so mad as to accept such a proposal! He wanted to live and return to his mother! Were they making fun of him? It wasn't the first time bullies asked him tricky questions so they would punish him when he selected the most logical choice._

 _When he looked into Dark's eyes however, something struck him. Hard. Dark was serious. He would fight with his dying breath, bleed, and finally triumph, all to achieve his purpose._

 _Tsuna was suddenly awed. It was as if he were looking into a mirror that showed the personification of your opposite. He had always wanted to be someone like Dark, strong, at ease but most of all sure of himself and of his decisions._

 _Dark sighed, got up and was about to go away._

 _He had apparently taken too long to consider and Dark must have perceived it as a decline of his offer!_

 _No!_

 _Tsuna had found his anchor in the storm and wouldn't absolutely let him go!_

 _He grabbed his hand stopping him from going away._

" _I want to come with you! Please!" He hadn't wanted to sound so desperate, but he instinctually know that going with Dark was essential for his future and happiness._

 _Dark looked startled at first, as if he couldn't believe his ears._

" _Are you sure?" His tone was so gentle it wade him even more convinced of the rightness of his choice. He just nodded energetically._

 _Red looked rather amused at his reaction._

" _See Kirito? You found yourself someone to travel with, and he's soooooo adorable! He looks like a cute little kitten!" Red even had the audacity to try to ruffle his hair after saying something like that! He growled at him, but felt Darks hand caress his hair, calming him down._

" _I'm Kirito, and the buffoon here is Klein-"_

" _Hey! I resent that! I am a perfectly serious samurai!" Kirito continued talking unruffled, as if he hadn't heard the indignant yell._

" _If you really want to come with me, we must go immediately."_

" _I'm Tsuna, and I'm looking forward to traveling with you"_

 _That was how his journey started._

 _In the future he would look back at this memory and think of this defining moment as the starting point of a path that defined his future, changed him irrevocably and finally give him happiness._

* * *

He woke up refreshed. The dream had resonated deep within him. It was probably his subconscious telling him he missed Kirito.

Well, he could easily solve this problem.

He picked up the phone, typed the number and waited. Kirito answered after the first ring.

* * *

Apparently Kirito's horrible family hadn't even deigned itself to pay a little more money (his grandfather was loaded, he owned hundreds of dojos!) so that he would be better taken care of in a hospital. Seriously! Just because Kirito preferred playing games, programming and computers than learning how to duel and therefore chose not to follow family traditions, didn't mean they had the right to treat him like trash! It was not like he was fooling around anyway! He had so much talent! He was even earning money with games! Tsuna betted that after acquiring his normal muscle mass and adjusting to the real world, Kirito would beat every sword master, even his grandfather!

Kirito was a hero! If it weren't for him thousands would have died!

* * *

They didn't talk much about their bad family situations but moved to better and happier topics.

His dream, happy memories and their plans for the future. Kirito hoped to finish High-School as fast as possible and then go to University and study Programming and Computer Engineering. He knew without doubt that Kirito would manage. He, on the other hand, was quite afraid. He didn't have good memories of school and he knew he was extremely behind kids his age. He had been taught quite a lot by other SAO players, so his knowledge was eclectic which was not very useful in the school system in which you had to learn specific topics. He really hoped to graduate and be able to enter Medicine.

They talked for hours about anything and everything until a nurse brought him lunch and he had to say goodbye to Kirito.

* * *

 _He felt bad, but he knew he had no choice. He could protect, teach and fight with one person, but more than one… It was going to be too dangerous, he couldn't assure every one's survival. He knew he was going to keep a very fast pace, so he could level up as soon as possible by completing the dangerous but highly remunerative quests._

 _Klein had a strange expression on his face and was staring wide eyed at something behind him._

" _You could take him, he certainly needs more help than I do"_

 _What?_

 _He turned._

 _At first he thought he was hallucinating. He knew the game was forbidden for people under thirteen and this child certainly wasn't older! He looked eight! The child looked like a small scared kitten, his huge honey doe-eyes were looking at them in fright and confusion._

 _He certainly did need help, he was too small to survive on his own and he doubted that many players were going to help him. After all, people, especially under pressure, would take advantage of him without remorse and Kitten would surely die._

 _He looked at him considering. He was just one person and he didn't seem troublesome or exuberant like Klein._

 _He needed him to calm down or he wouldn't consider his offer with a clear mind. He walking towards him, crouched down and looked at him strait in the eyes._

 _Kitten seemed more at ease now but he knew he couldn't afford to coddle him, Kitten had to understand the seriousness of the situation._

" _Would you like to stay here in the city, safe from harm, or come with me? If you chose to come know that your future will be filled with danger, terrifying and difficult but I will look after at the best of my abilities. I will fight until I manage to beat this game and escape."_

 _Maybe he had been too harsh in formulating his proposal but he wouldn't it withdraw or soften his request. He had stated the truth._

 _Kitten looked even more terrified than before and was staying quiet._

 _He sighed, he had tried but he wouldn't force him to come. He got up resignedly and was about to go away but apparently he had misjudged Kitten's actions._

" _I want to come with you! Please!" He sounded so distressed while grabbing his hand tightly, it was as if he was used to people leaving him._

" _Are you sure?" He tried to sound as kind as he could as to calm his frantic emotions. If only Klein wasn't so annoyingly insensitive._

" _See Kirito? You found yourself someone to travel with, and he's soooooo adorable! He looks like a cute little kitten!" Kirito had the urge to smack his face in desperation… or maybe smack Klein… Yes that looked much more appealing. Although it seemed Klein saw the same resemblance he had seen in Kitten._

 _He had the most unusual urge to hug Kitten as soon as he heard his adorable little growl. He controlled himself by passing his hand trough the child's incredibly soft and fluffy hair._

" _I'm Kirito, and the buffoon here is Klein-"_

" _Hey! I resent that! I am a perfectly serious samurai!" He pretended not to have heard him._

" _If you really want to come with me, we must go immediately."_

" _I'm Tsuna, and I'm looking forward to traveling with you"_

 _That was how their journey started._

 _He would never had thought that this adorable little child would come to mean so much to him that he would give his loyalty, life and heart._

* * *

Kirito woke up to the ring of his phone. He picked it up, hoping to hear his Little Lion.

Tsuna answered.

Sometimes he thought that they must be connected in some way. The manner in which they understood each other was astonishing. Asuna used to say that they must be connected telepathically. He totally agreed. How could he not after understanding Tsuna so well, fighting in such a coordinate way it seemed they were dancing to a music only they knew, translating Tsuna's gestures, moods and actions so perfectly that sometimes they didn't even need to talk?

* * *

 **A.N.**

 **Soooo…did you like it?  
**

 **A big thank you to everyone who favored and followed this story!**

 **I really liked your reviews! Thanks to** **CreepyAlis** **,** **aftereight8.18** **, Guest, Ashley,** **Ryuu and Nats** **u,** **MrGarcia37** **and Guest.**

 **Answers:**

 **Ashley** **:**

I'm sorry but I think that neglecting a child cannot be excused, so I'll just show things how they are, without intentional bashing. As for Iemitsu, he will not suddenly change lifestyle, he hasn't been part of the family since… never… and therefore won't be in the future. I don't know if he will appear in other moments and as something different than a father. We'll see…

 **Ryuu and Nats** **u:**

Thank you for the cookies! I ate them all! (thank Heavens I'm immortal or I would have exploded)

 **MrGarcia37** **:**

Kirito is 16, he started playing a 13 and the game ended when he was 16 (one year later than Canon because they had to complete all the 100 floors). Tsuna is 13, he started playing at ten.

* * *

 **ALERT! Hint/spoiler!**

 **I'm not going to give Kirito some strange and mysterious flame. Which one do you think he has?**

* * *

 **And seriously nobody cares who will Asuna be with? Shall I chose?**


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